With the increased concern regarding bioterrorism and the need to promote homeland security, it is critical to have a method for the rapid detection and identification of biological agents that could be used for terrorism.
The use of nuclear quadrupole resonance (NQR) as a means of detecting explosives and other contraband has been recognized for some time, see e.g. T. Hirshfield et al, J. Molec. Struct. 58, 63 (1980), A. N. Garroway et al, Proc. SPIE 2092, 318 (1993), and A. N. Garroway et al, IEEE Trans. on Geoscience and Remote Sensing 39, 1108 (2001). NQR provides some distinct advantages over other detection methods. NQR spectroscopy can detect and discriminate specific solid state materials containing quadrupole nuclei, i.e. nuclei with a quadrupole moment. As with nuclear magnetic resonance (NMR), a radio frequency coil produces an oscillating magnetic field at a frequency identified with a specific compound containing one or more quadrupole nuclei. If the specific compound is present a return NQR signal is detected. Unlike NMR, NQR requires no static magnetic field. NQR spectroscopy is extremely cost effective since it is a radio frequency (RF) technique in a frequency region where silicon based electronics operate. NQR detection systems use non-ionizing magnetic fields near 5 MHz, and therefore present no health hazards to nearby workers and will not damage materials sensitive to ionizing radiation. The average power of the applied oscillating magnetic field in a NQR detection system is about 100 Watts, and it can thus operate from standard alternating current (AC) electrical outlets (either 110 V or 240V).
A number of fundamental problems exist for the conventional approach to NQR spectroscopy. These problems result in low throughput and long measurement times. The use of high temperature superconductor (HTS) self-resonant structures, particularly HTS self-resonant receive coils, i.e. sensors, dramatically improves the sensitivity of the NQR spectrometer. For example, the high quality factor Q of an HTS sensor results in a 5–20 dB improvement in the signal-to-noise ratio (S/N) as compared to a conventional sensor. This is important in view of the low intensity NQR signal. HTS enhanced NQR systems have been scientifically demonstrated for the detection of macroscopic samples of contraband such as explosives and drugs.
The object of this invention is to use HTS enhanced NQR systems to provide a method for detecting biological agents, particularly those that could be used for bioterrorism.